As a conventional example of vehicle-mounted power conversion devices, Patent Document 1 has been known. A cabinet of a vehicle-mounted power conversion device used in Patent Document 1 is divided into two parts, i.e., a first cabinet 1 located at a lower position and a second cabinet 2 located at an upper position.
In the housing space of the first cabinet 1, a power module 3 and a capacitor 4 are housed. At a part above the power module 3 and the capacitor 4, a bus bar 5 and a power module substrate 6 are disposed. The second cabinet 2 defines an upper housing space and a lower housing space with a partition wall 2a, and the above-mentioned bus bar 5 and the power module substrate 6 are housed in the lower housing space of the second cabinet 2. In the upper housing space of the second cabinet 2, a control substrate 7 is disposed. The control substrate 7 is connected to the power module substrate 6 disposed in the lower housing space of the second cabinet 2, through a harness (not shown illustrated) provided piercing through a through hole 2b formed in the partition wall 2a. 